Messages in this thread | | | Date | Fri, 17 May 2002 14:30:52 -0700 | Subject | Question : Broadcast Inter Process Communication ? | From | Jean Tourrilhes <> |
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Hi everybody,
I was looking under Linux for a mechanism to distribute an event from one process (a daemon) to a set of other processes (deamons or applications). The number and indentity of those other processes would not be known by the process generating the event, those processes would register themselves dynamically to the stream of event. And the event need to be delivered to all of them (not only the first one). In other words, it would look like a *broadcast* message queue, where the sender process would create the queue and write events to it, and the other bunch of processes would dynamically open the queue and listen for events. My first attempt was with IPC message queues, but my experimentations show that only the first receiver get the message. It is pretty clear that no amount of tweaking will get the IPC message queue to behave like that : IPC message queues don't have a notion of receiver session, so can't send message to all receivers. I can't use signals because signals are unicast, and I don't want the sender to have to manage a list of processes it has to send signals to. Also, signals don't have payload and are synchronous. Unix sockets don't have a broadcast mode, and therefore are limited to a single receiver (actually, I think you can only have one sender). In theory, you could implement a broadcast mode for Datagram sockets using the current API, it's just not done today. I don't really want to use a UDP broadcast socket for efficiency reason (and also because I don't want those events to go accidentally over the network, or beeing succeptible to receive spoofed events from the network). Also, it require the network stack to be active and properly configured. But I must admit a UDP broadcast on the loopback does pretty much what I need. Failing that, I could hack a kernel module to do that, but I don't want to re-invent the wheel...
This "one sender - multiple reader" model seems common and usefull enough that there must be a way to do that under Linux. I know that it exist under Windows. Can somebody help me to find out how to do it under Linux ? Thanks in advance...
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